My iPhone is not new, but something thinks it is (ITunes i think)

My iPhone seems to be registered as new, when I connect my iPhone (6s) to my MacBook (pro) this is all that showes up (it is in norwegian; "welcome to your new iPhone" it basically says that your options are to either configure your iPhone as new, or restore from backup. I have had my iPhone for a while now. I am originally trying to update to IOS 11, but find myself unable to do so through just my phone, it only gets stuck at "verifying update". And it takes such a long time that I have to just shut it of completely, then turn it back on and still not being able to get any further. I am therefore trying to update through iTunes, and am now stuck with this problem too.

please help me.